Compared with White adults, Non-Hispanic Black adults are at an elevated risk of developing cardiovascular disease (CVD) and end-stage chronic kidney disease (CKD) two of the leading causes of mortality in the United States (U.S.). Inadequate hydration status is associated with all-cause mortality and several risk factors for CVD and CKD including obesity, insulin resistance, hypertension, and metabolic syndrome. Prior data demonstrate Black American individuals are more likely to be hypohydrated (i.e., inadequately hydrated) when compared with White individuals. One study in emerging adults (18-25 years old) indicates that Black adults are more likely to be hypohydrated compared with White adults when assessed using gold-standard 24-hour urine collections. Socioeconomic factors influence hydration practices. For example, there are well-justified increased perceptions of unsafe tap water among racial and ethnic minorities. Indeed, the recent Flint, Michigan, and Jackson, Mississippi water crises have raised public awareness over these environmental injustices and ways to increase safe drinking water availability and access. However, there remains a critical need for empirical studies on 1) strategies to address racial disparities in hydration and resultant health consequences; and 2) the role socioeconomic factors in contributing to hydration.
Importantly, hypohydration is associated with increased production of arginine vasopressin (AVP), a peptide hormone produced in the hypothalamus that influences body water balance via anti-diuretic effects. Plasma copeptin is an established surrogate marker of circulating AVP concentration. Plasma copeptin is associated with incident type 2 diabetes, metabolic syndrome, the progression of CKD, and CVD. Some, but not all, studies have demonstrated racial differences in circulating AVP/copeptin. Further, prior studies that aimed at increasing water resulted in reductions in copeptin and improvements in cardiometabolic health. For example, in a cohort with high plasma copeptin, increased water intake also reduced fasting plasma glucose. In a cohort of adults with overweight and obesity, increased water or low-calorie beverage intake reduced fasting plasma glucose and contributed to modest weight loss. Lastly, over 90% of adults do not meet recommendations for potassium intake. Importantly, potassium improves blood pressure (BP), particularly in Black adults, who tend to consume less potassium and have higher BP. Yet, there remains a knowledge gap regarding whether hydration intervention(s) inclusive of water (with or without) potassium could attenuate racial disparities in hydration status and circulating AVP/copeptin. Therefore, the investigators are seeking to test the investigators' central hypothesis that water with a potassium supplement (2000mg/day) will improve hydration and cardiovascular health in White adults (n = 20, 10 females, 10 males), and to a greater extent in young Black Adults (n = 20, 10 females, 10 males). The investigators will utilize three complementary specific aims to address the investigators' hypotheses:
Aim 1: Determine whether water with potassium supplementation improves hydration status and reduces circulating copeptin. The investigators hypothesize that water and potassium supplementation will improve hydration and renal biomarkers, including increased urine volume, and reduced urine specific gravity, urine osmolality, and plasma copeptin.
Aim 2: Determine whether water with potassium supplementation improves BP and vascular health. The investigators hypothesize that water and potassium supplementation will reduce resting laboratory BP and ambulatory BP (awake, asleep, and nocturnal BP dipping), and reduce arterial stiffness assessed via pulse wave velocity.
Aim 3: Determine whether socioeconomic factors are associated with hydration perceptions, knowledge, and practices. The investigators hypothesize that area deprivation index (ADI, i.e., more deprivation) will be associated with hydration perceptions (e.g., greater distrust of tap water) and inadequate hydration assessed by self-reported fluid intake and urine-specific gravity.
In summary, a knowledge gap remains in determining the underlying reasons for the consistently reported racial differences in hydration. To restate, the purpose of this study is to determine 1) whether prescribing water with potassium supplementation is efficacious at improving hydration and reducing plasma copeptin in Black and White adults; 2) whether improving hydration with supplemental potassium improves BP and vascular function in young Black and White adults; 3) Another area of innovation in the investigators' proposal is determining whether area deprivation index (ADI, i.e., more deprivation) is associated with and 3a) beliefs and practices around hydration and 3b) hydration status. 4) We also seek to determine whether the intervention leads to greater improvements in Black adults who are more likely to be underhydrated.
